1,395 research outputs found
Searching for cavities of various densities in the Earth's crust with a low-energy electron-antineutrino beta-beam
We propose searching for deep underground cavities of different densities in
the Earth's crust using a long-baseline electron-antineutrino disappearance
experiment, realized through a low-energy beta-beam with highly-enhanced
luminosity. We focus on four cases: cavities with densities close to that of
water, iron-banded formations, heavier mineral deposits, and regions of
abnormal charge accumulation that have been posited to appear prior to the
occurrence of an intense earthquake. The sensitivity to identify cavities
attains confidence levels higher than and for exposures
times of 3 months and 1.5 years, respectively, and cavity densities below 1 g
cm or above 5 g cm, with widths greater than 200 km. We
reconstruct the cavity density, width, and position, assuming one of them known
while keeping the other two free. We obtain large allowed regions that improve
as the cavity density differs more from the Earth's mean density. Furthermore,
we demonstrate that knowledge of the cavity density is important to obtain
O(10%) error on the width. Finally, we introduce an observable to quantify the
presence of a cavity by changing the orientation of the electron-antineutrino
beam, with which we are able to identify the presence of a cavity at the
to C.L.Comment: 7 pages, 5 figures; matches published versio
Superconducting and Normal State Properties of Neutron Irradiated MgB2
We have performed a systematic study of the evolution of the superconducting
and normal state properties of neutron irradiated MgB wire segments as a
function of fluence and post exposure annealing temperature and time. All
fluences used suppressed the transition temperature, Tc, below 5 K and expanded
the unit cell. For each annealing temperature Tc recovers with annealing time
and the upper critical field, Hc2(T=0), approximately scales with Tc. By
judicious choice of fluence, annealing temperature and time, the Tc of damaged
MgB2 can be tuned to virtually any value between 5 and 39 K. For higher
annealing temperatures and longer annealing times the recovery of Tc tends to
coincide with a decrease in the normal state resistivity and a systematic
recovery of the lattice parameters.Comment: Updated version, to appear in Phys. Rev.
Neutrino-nucleus interaction rates at a low-energy beta-beam facility
We compute the neutrino detection rates to be expected at a low-energy
beta-beam facility. We consider various nuclei as neutrino detectors and
compare the case of a small versus large storage ring.Comment: 6 pages, 3 figure
Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations
Recently there has been much interest in optomechanical devices for the
production of macroscopic quantum states. Here we focus on a proposed scheme
for achieving macroscopic superpositions via nested interferometry. We consider
the effects of finite temperature on the superposition produced. We also
investigate in detail the scheme's feasibility for probing various novel
decoherence mechanisms.Comment: 12 pages, 2 figure
Intermediate energy Coulomb excitation as a probe of nuclear structure at radioactive beam facilities
The effects of retardation in the Coulomb excitation of radioactive nuclei in
intermediate energy collisions (Elab ~100 MeV/nucleon) are investigated. We
show that the excitation cross sections of low-lying states in 11Be,
{38,40,42}S and {44,46}Ar projectiles incident on gold and lead targets are
modified by as much as 20% due to these effects. The angular distributions of
decaying gamma-rays are also appreciably modified.Comment: 21 pages, 3 figures, Phys. Rev. C, in pres
Are environmental characteristics in the municipal eldercare, more closely associated with frequent short sick leave spells among employees than with total sick leave: a cross-sectional study
Background: It has been suggested that frequent-, short-term sick leave is associated with work environment
factors, whereas long-term sick leave is associated mainly with health factors. However, studies of the hypothesis of
an association between a poor working environment and frequent short spells of sick leave are few and results are
inconsistent. Therefore, we aimed to explore associations between self-reported psychosocial work factors and
workplace-registered frequency and length of sick leave in the eldercare sector.
Methods: Employees from the municipal eldercare in Aarhus (N = 2,534) were included. In 2005, they responded to
a work environment questionnaire. Sick leave records from 2005 were dichotomised into total sick leave days (0–14
and above 14 days) and into spell patterns (0–2 short, 3–9 short, and mixed spells and 1–3 long spells). Logistic
regression models were used to analyse associations; adjusted for age, gender, occupation, and number of spells or
sick leave length.
Results: The response rate was 76%; 96% of the respondents were women. Unfavourable mean scores in work
pace, demands for hiding emotions, poor quality of leadership and bullying were best indicated by more than 14
sick leave days compared with 0–14 sick leave days. For work pace, the best indicator was a long-term sick leave
pattern compared with a non-frequent short-term pattern. A frequent short-term sick leave pattern was a better
indicator of emotional demands (1.62; 95% CI: 1.1-2.5) and role conflict (1.50; 95% CI: 1.2-1.9) than a short-term
non-frequent pattern.
Age (= 40 years) statistically significantly modified the association between the 1–3 long-term sick leave
spell pattern and commitment to the workplace compared with the 3–9 frequent short-term pattern.
Conclusions: Total sick leave length and a long-term sick leave spell pattern were just as good or even better
indicators of unfavourable work factor scores than a frequent short-term sick leave pattern. Scores in commitment
to the workplace and quality of leadership varied with sick leave pattern and age. Thus, different sick leave
measures seem to be associated with different work environment factors. Further studies on these associations may
inform interventions to improve occupational health care
The implications of noninertial motion on covariant quantum spin
It is shown that the Pauli-Lubanski spin vector defined in terms of
curvilinear co-ordinates does not satisfy Lorentz invariance for spin-1/2
particles in noninertial motion along a curved trajectory. The possibility of
detecting this violation in muon decay experiments is explored, where the
noninertial contribution to the decay rate becomes large for muon beams with
large momenta and trajectories with radius of curvature approaching the muon's
Compton wavelength scale. A new spacelike spin vector is derived from the
Pauli-Lubanski vector that satisfies Lorentz invariance for both inertial and
noninertial motion. In addition, this spin vector suggests a generalization for
the classification of spin-1/2 particles, and has interesting properties that
are applicable for both massive and massless particles.Comment: REVTeX file; 7 pages; 2 figures; slightly revised with new abstract;
accepted for publication in Classical and Quantum Gravit
A Deeper Look at Student Learning of Quantum Mechanics: the Case of Tunneling
We report on a large-scale study of student learning of quantum tunneling in
4 traditional and 4 transformed modern physics courses. In the transformed
courses, which were designed to address student difficulties found in previous
research, students still struggle with many of the same issues found in other
courses. However, the reasons for these difficulties are more subtle, and many
new issues are brought to the surface. By explicitly addressing how to build
models of wave functions and energy and how to relate these models to real
physical systems, we have opened up a floodgate of deep and difficult questions
as students struggle to make sense of these models. We conclude that the
difficulties found in previous research are the tip of the iceberg, and the
real issue at the heart of student difficulties in learning quantum tunneling
is the struggle to build the complex models that are implicit in experts'
understanding but often not explicitly addressed in instruction.Comment: v2, v3 updated with more detailed analysis of data and discussion;
submitted to Phys. Rev. ST: PE
- …